Figure 311

Diagnostic approach to hypokalemia: hypokalemia due to renal losses with metabolic alkalosis. The urine chloride value is helpful in distinguishing the causes of hypokalemia. Diuretics are a common cause of hypokalemia; however, after discontinuing diuretics, urinary potassium and chloride may be appropriately low. Urine diuretic screens are warranted for patients suspected of surreptious diuretic abuse. Vomiting results in chloride and sodium depletion, hyperaldosteronism, and renal potassium wasting. Posthypercapnic states are often associated with chloride depletion (from diuretics) and sodium avidity. If hypercapnia is corrected without replacing chloride, patients develop chloride-depletion alkalosis and hypokalemia.